Historical Views of Invariance: Evidence from the Measurement Theories of Thorndike, Thurstone, and Rasch

The purpose of this study is to provide a historical perspective on the concept of invariance within measurement theory. Two major classes of invariant measurement are described—sample-invariant item calibration and item-invariant measurement of individuals. The work of Stevens is used to help clarify the concept of invariance. The importance of invariance as a key measurement concept is then illustrated with the measurement theories of Thorndike, Thurstone, and Rasch. A case is made for viewing invariance as a fundamental aspect of measurement in the behavioral sciences; invariance appears to be essential in order to realize the advantages of objective measurement.